Filtering apparatus for liquids



July l0, 1951 J. P. BUFFLE FILTERING APPARATUS FOR LIQUIDS Filed Dec. 3. 1946 @@@QQCDCDCDQ Patented July 10, 1951 FILTERING APPARATUS FORLIQUIDS Jean Philibert Buffle, Geneva, Switzerland, as'- signor to Services Industriels de Geneve, Geneva, Switzerland, a corporation Application December 3, 1946, SerialNo. 713,714 YIn Switzerland June v17,1946

6 Claims. (Cl. 210-130) The present invention relates to a filtering apparatus fory liquids.

Filtering of liquids is generally carried out by means of open or closed sand lters, functioning either by gravity or under pressure. The cleansing of the lter layer is effected either with puried liquid sent under pressure in a countercurrent or with a mixture of the latter with compressed air. In the second case, the filter mass may be treated successively with the two iiuids.

The apparatus and processes of iiltering in current use present the following various drawbacks:

(a) Undesirable agitation of the filter mass at the entry point.

(b) Undesirable variations in ltration speed along the cross-section of the lter mass.

(c) More mechanical strength of prior used filtering surfaces.

(d) Undesirable free space not contributing to the'ltering function.

(e) The use of metal filtrate containers.

(f) The unequal distribution of the compressed air and the compressed cleansing liquid, under the bottom, at the moment of the elimination of the matter in suspension retained by the filter mass.

v(g) The use in certain devices of a single piping for the compressed air and the compressed cleansing liquid.

(h) The requirement of large quantities of Washing liquid due to the small capacity of the liquid evacuating parts.

These various drawbacks result in sometimes obtaining an imperfectly filtered liquid, and in the exaggerated fouling of the lter mass. They also lead to the unequal distribution of the matter in suspension retained by the lter mass, which makes diiicult the elimination of this matter in suspension from the lter mass, and causes an exaggerated consumption of cleansing liquid.

The present invention aims at obviating these drawbacks and it relates to a liquid-iiltering apparatus which'is characterised in that'it comprises a tank in which a slab of porous substance is placed, the upper face of which is'fiat and smooth and on which a granular filter mass lies, while its lower face presents cells with no direct communication with one another, this slab being supported by a watertight floor or support which closes the said cells, with, on the one hand, water-flow tubes going through said watertight floor and opening into the cells,next

' to the part of fthev slab forming their: base, and, 'onthe other'hand'byf additional tubes the upper "2 end of whichopens into cavities provided for in the lower surface of the slab which makes up the ceiling of thecells, said additional tubes being used for .the issue of gas in the aforesaid cavities, during the Lcleansing of the device.

The appended .drawing represents, diagrammatically and in the way'of an example, one embodiment of the apparatus according to the inf vention.

Figure 1 is a vertical section of the apparatus;

Figures 2, 3 an'd4 are details ofit, the latter on kan enlarged scale.

The apparatus represented comprises a tank I containing, about halfway up, -a slab 2 of a porous substance, preferably porous concrete, the upper face 3 of 4which is flat andsmooth. This slab is made up of component units 4 placed side by side. Figure 2 represents one of these units asseen iromunderneath; each of the units 4 presents, onrits lower face, a recess 5 and, at thebottom of .this.cell, a .series ofcavities 6 arranged as 'is shown in Figures 2 and 4. The border of the lower face ofthe unitsvll, designated by 1, rests on a watertight floor which consists of slabs 8 in waterproof concrete, placed side by side as .is Shownin the drawing. Means for ensuring watertightness are provided on the border l ofthe lower faceof the slab, vso that no direct communicationexists betweenl thedifferent cells. Further watertight means 9 .are provided between the different units .8 4of the watertight floor and betweenthese units .8 .and the side-walls of the tank I. Watertight means I0 lare also provided between a shelf II Vof the tank and thev units v8 which are supported by. this shelf.

Figure V3 is a plan of one-of the .units 8.0i the iloor supporting the slab 2. Eachiof the units is traversed by a series of Aauxiliary .tubes I2, of a non-metallicsubstance, open at their two ends and lled with: porous concrete I3. The upper portion-of each one'of the auxiliary tubes I2 opens, very close to the porousslab, into one of the cavities vIi. The lower portion of these tubes descends into thelower--region of the tank.

Finally, a series of tubes I4 extends through each of the unitsr. The upper ends of these tubes open flush with theupper face of the .units 8, while their lower end opens into thebottom region of the tank I.

The additional tubes I2,as Well as the cavities 6 into which they penetrate, are arranged in a regular pattern as is shown in Figures L2 and 3.

.-A iilter 'mass I5, consisting Yof fsand, lies on the uppersurfa'ce ofthe slab-2.

3 Pipes i6 lead into the upper region of the tank I, while a pipe II opens into the bottom of the latter.

The apparatus represented operates as follows:

(ai) Filtration phase The liquid tovbe filtered, loaded with matter in suspension, is poured on to the mass I by a device not represented ensuring as uniform a distribution as possible and avoiding the formation of eddies. The liquid first goes through the filter mass I5, which retains the matter in suspension, then, once it is completely rid of this matter, it passes through the porous upper slab 2, which should not exercise any retentive effect. The flow through this porous slab occurs in a practically uniform manner throughout its whole surface, even close to the sides of the tank. The liquid having thus passed through the slab gathers on the false bottom consisting of the units 8 of the floor supporting the slab. Thence it flows into the collector chamber i8, formed by the lower region of the tank, through the tubes I4 and through the interior of the additional tubes IZ-i. e., by traversing the porous conglomerate which fills them-the larger part of the liquid owing, however, through the tubes i4. From there, the ltered liquid escapes by way of the pipes Il'.

(b) Regeneration phase After the apparatus has been working for a certain time, it is necessary to clear the filter mass I5 of the impurities that were in suspension in the liquid that has been filtered and which the mass had retained. To proceed with this regeneration of the filter mass l5, the pipe I'l for evacuating the purified liquid is closed and the liquid covering the filter mass is evacuated. Compressed air is introduced into the collector chambeiv I8. This air accumulates under the false bottom V8 and, the instant it reaches the base of the additional tubes I2, this air finds a way out through the porous conglomerate I3 with which these tubes are filled and escapes at their top in the form of a multitude of fillets issuing into the cavities of the recesses 5. From there, this air continues its upward course in a multitude of threads through the porous slab 2, which it leaves in provoking a stirring-up throughout the filter mass I5. During that part of the process of regeneration, and the following wherein anV air current and a water flow are simultaneously vintroduced into the false bottom, the water-level remains invariably xed with that of the base of the porous mass I3. As a result, air can only escape through the porous mass I3 and never through the tubes I4. The filter mass, violently agitated by the air issuing from the different additional tubes I2, separates itself from the impurities that it had extracted from the liquid. Afterwards, liquid purified beforehand and proceeding from a special container not represented is sent, under pressure, into the collector chamber I8. This liquid escapes upwards through the Vtubes I4 (which extend lower down than the bottom ends of the additional tubes l2), arrives in the recesses 5 and, pursuing its upward course, traverses the porous slab 2. During this time, the air continues to pass through the additional tubes I2 and through the slab 2 without being hampered in any way.

This simultaneous action of the air and the liquid has the effect of carrying towards the top of the tank the matter that the'niass 'I5 had retained, whereas the mass itself, consisting of a denser substance, remai-ns in the lower part of the space situated above the slab 2. This filter mass continues, notwithstanding that, to be constantly agitated. When the cleansing liquid loaded with matter in suspension reaches a certain level, Vthe intake of air -is stopped, a pause is made to allow the grains of the filter mass to settle and then the evacuation pipes I6 are opened. These latter, acting as a siphon, suck in the cleansing liquid loaded with al1 the matter in suspension which has been extracted from the filter mass I5 to the exclusion of the grains of the latter, which cannot be drawn up so high by the cleansing liquid because of their too great density. During the whole of this operation, the cleansing liquid continues to iiow upwards from the bottom of the tank. The operation is stopped when the cleansing liquid is perfectly limpid.

The washing phase can be repeated immediately if the filter mass is not entirely rid of its impurities. When the regeneration phase is terminated, the filter mass automatically resumes its position and immediately presents a horizontal surface. The apparatus can then be set working again forthwith.

If the filtering operations are properly carried out and the lter mass, which must be perfectly adapted to its purpose, correctly and thoroughly cleansed after each filtration phase, there is no risk of fouling the porous slab. Its porosity should never vary, even after years of service.

The entire operations of filtration and elimination of the matter in suspenion may be rendered wholly automatic.

So that the slab 2 of porous concrete shall possess the requisite degree of porosity, the proper process for its manufacture would be as follows:

Perfectly screened ne gravel should be obtained which has passed through, for example. the Ll-mm. sieve (square mesh) but been refused by the 2-mm. sieve. This fine gravel, which must be as homogeneous as possible from the point of view of its chemical composition, should be thoroughly washed and dried.

To prepare the porous concrete, 250 to 300 parts of this dry gravel is to be thoroughly mixed with perfectly homogeneous grout obtained by mixing 40 to 50 parts of a special cement possessing high physical resistance with 20 to 30 parts of water.

After prolonged stirring, suitable moulds are filled, completely closed so as to avoid too-rapid evaporation; the concrete is pressed down with s, a trowel, then left to set and it can be turned out of the mould three days after,

As regards the filter mass I5, it may consist of any granular substance suiciently hard to resist exaggerated wear by the regeneration operation. The granulometry of this material should be perfect, the maximum variations from the diameter chosen not exceeding 15% more or less. According to the degree aimed at-pre-filtration or fine filtration-which is determined by the filtering speed the most appropriate, a sub-v stance should be chosen the diameter of which ranges between the minimum of 0.5 mm. and the maximum of 1.2 mm. A

What I claim is:

l. A liquid-filtering apparatus comprising a tank, a slab of a porous substance in said tank, the upper face of said slab being flat and smooth, a granular filter mass positioned on said upper face, the lower face of said slab having recesses therein with no direct communication with one another, said slab having cavities therein opening into said recesses, a watertight support in said tank supporting said slab closing said recesses, water-flow tubes extending through said watertight support and opening into said recesses, and additional tubes extending through said support having their upper ends extending into said cavities, said additional tubes being used for the issue of gas into said cavities, during regeneration.

2. An apparatus as set forth in claim 1, wherein said slab is constructed of porous concrete.

3. An apparatus as set forth in claim 1, wherein said slab is formed of component units of porous concrete placed side by side.

4. An apparatus as set forth in claim 1, wherein said slab is formed of component units of porous concrete placed side by side and wherein the diierent units forming said slab are provided, at their lower ends, with watertight members placed between said units and said support to seal direct communication between said recesses.

5. An apparatus as set forth in claim 1, wherein said support is formed of several component units placed side by side and watertight members are provided between said units and between said units and said tank.

6. An apparatus as set forth in claim 1, wherein said additional tubes for the issue of gas are formed by tubes lled with porous concrete.

JEAN PHILIBERT BUFFLE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

